MIAMI — Fighting to curry favor with Florida’s large pool of Hispanic voters, Newt Gingrich on Wednesday called for a guest-worker program for most illegal immigrants, but his campaign could not say whether those people would be on a path to citizenship — the key question in the immigration debate.

Under close questioning by Univision’s political host, Jorge Ramos, Mr. Gingrich said he would grant quick citizenship rights to illegal immigrants who join the military or to those who have been in the U.S. between 20 and 25 years. He said the rest of the estimated 11 million should be given access to a guest-worker program.

“With most of them? I would urge them to get a guest-worker permit,” he said, calling for a substantial rewrite of immigration laws that would cancel existing penalties and instead let illegal immigrants stay.

But his campaign said it was unclear whether at the end of that guest-worker period the immigrants would be allowed to stay and gain citizenship, essentially jumping the legal immigration line, or whether they would be required to return home.

If the guest workers would be required to go home, then Mr. Gingrich’s position is similar to that of Republican primary rival Mitt Romney, who also has called for a transition period for illegal immigrants, during which they could stay and work while they get their affairs in order, but they would eventually have to go home.

If Mr. Gingrich envisions a path to citizenship for guest workers, then his plan is closer to President Obama‘s, who has called for a chance for nearly all illegal immigrants to become citizens at the end of a multistep process.

The issue is important for the Hispanic Republican electorate in Florida, which is estimated at more than 450,000 strong — making it a key voting bloc in the pivotal Florida GOP primary next week.

Just as important, the GOP presidential candidates have vowed to make a play for Hispanic votes in the general election, where analysts say Republicans must win at least 40 percent — the same amount that helped George W. Bush win re-election in 2004. In 2008, Sen. John McCain of Arizona won 31 percent of the Hispanic vote, losing the state and the election.

The four remaining major candidates for the GOP’s nomination — Rep. Ron Paul and former Sen. Rick Santorum round out the field — square off Thursday in a debate aired by CNN and the network’s Spanish-language station. It is being co-sponsored by the Hispanic Leadership Network.

Mr. Gingrich and Mr. Romney traded jabs throughout the day on the issue in a back-and-forth highlighted by Mr. Gingrich’s decision to pull down a campaign advertisement from his camp that called Mr. Romney “anti-immigrant,” after coming under fire by Sen. Marco Rubio, Florida Republican, and high-profile Romney surrogates from the Miami area.

Both men also appeared at a president’s forum co-sponsored by Univision, the largest Spanish-language television network in the nation, and the U.S. Hispanic Chamber of Commerce.

Immigration is a major issue but not the only one for Hispanic Republicans in Florida. Many voters are Cuban and enjoy special carve-outs in immigration law, though they do have sympathy for fellow Hispanics who are more intimately touched by illegal immigration. Indeed, many Cuban-American Republican leaders support passage of the Dream Act to legalize illegal-immigrant young adults who are going to college or joining the military.

“The Cubans do not have the problem of immigration, but we are sympathetic to others in this country who have been here for years and who want some kind of resolution of the issue. But having said that, this is a country of law; you cannot come here without anyone knowing who you are and stay here because you want to and not be identified,” Remedios Diaz-Oliver, of the US-Cuba Democracy PAC, told The Times.

She said the Dream Act is the one issue where she disagrees with Mr. Romney — as do Reps. Mario Diaz-Balart and Ileana Ros-Lehtinen and former Rep. Lincoln Diaz-Balart, former Sen. Mel Martinez and former U.S. Commerce Secretary Carlos Gutierrez — but all of them back Mr. Romney.

“Neither Gingrich, Santorum or anybody is with the Dream Act. If the Dream Act will be a factor, let them vote for Obama, who will promise but not do anything,” Ms. Diaz said.

Still, any talk of legalization is a touchy issue among broader Republican primary voters. In Iowa and South Carolina, nearly every town-hall event featured at least one person asking the candidates how they would gain control of the U.S.-Mexico border and how they would handle the illegal immigrants already here.

Texas Gov. Rick Perry, a onetime front-runner in the campaign, saw his fortunes collapse when fellow candidates attacked him for signing a bill giving illegal-immigrant college students in-state tuition rates in Texas.

In Florida on Wednesday, Mr. Gingrich ridiculed Mr. Romney’s call for “self-deportation,” saying the approach lacks “humanity” and arguing that it is unrealistic for him to think stronger enforcement of the nation’s laws will persuade illegal immigrants to leave the nation voluntarily.

“For Romney to believe that somebody’s grandmother is going to be so cut off she is going to self-deport — this is an Obama-level fantasy,” he said.

Mr. Romney countered later in the day by saying Mr. Gingrich was trying to pander to Hispanic voters and hide the fact he, himself, used to argue that self-deportation was the proper solution to illegal immigration.

The interviews coincided with the release of a new Univision, ABC News and Latino Decisions poll that showed Mr. Obama holds significant leads over his potential GOP rivals among Florida Hispanics, while Mr. Romney leads his Republican competitors among the same voters in the nomination race in Florida.

Asked about his poor showing in the poll, Mr. Gingrich said that at this stage in the 1980 presidential campaign Jimmy Carter was beating Ronald Reagan by 30 percentage points and that by the time the race moves into the fall, Hispanic voters will move in his direction once they realize they like his values, job creation record and his stance on Cuba.

“I have a hunch that, by this fall, we may do better than any Republican except maybe Reagan,” he said.